Numbers beginning with 615-685

Clarksville, a city in and the county seat of Montgomery County, Tennessee, and the fifth-largest city in the state behind Memphis, Nashville, Knoxville, and Chattanooga, respectively. The city had a population of 132,957 at the 2010 census, and an estimated population of 142,519 in 2012. Clarksville is the fifth-fastest growing city in the nation, of cities with a population over 50,000. source

Area codes 615 and 629 are area codes in Tennessee serving Nashville (Davidson County) and the 12 surrounding counties. 615 is the main area code, while 629 is an overlay covering the same area that will begin service in 2014. Besides Nashville, Murfreesboro, Franklin, Hendersonville, and Lebanon are other major cities in the 615/629 service territory. source